Besides the products they offer at their website, there does not appear to be a fixed rate for adhoc coding work that they do. It's been hit and miss for me. Write to Patryk at info@bimmer-tech.net and he will give you a quote.

Not sure about how strictly they adhere to the warranty conditions where you are. For me, I had my BMW dealer workshop install the cabling work that came with the 6NR kit from BimmerTech without any issues. I swapped the 6WB cluster on my own. Also did a bunch of coding both by BimmerTech and myself. So far no issues with the vehicle or the warranty.

One thing's for sure. You will get more out of your vehicle each time you add a coding if you are into the automation and gadgetry that adorn it.